1. Field of the Invention
This invention relates to the production of hydrogen by reforming a petroleum oil fraction. More specifically, the invention is directed to a process of deriving hydrogen from a kerosene fraction in which kerosene is stripped of its sulfur contents by means of a hydrogenative desulfurization catalyst, a hydrogen sulfide absorbent and a nickel sorbent and subjected, with addition of water, to reforming reaction on a steam reforming catalyst.
2. Prior Art
Generally, hydrogen finds wide application for instance as a starting material, a fuel, a refining agent and the like and is made available by a variety of processes including electrolysis of water and steam reforming, partial oxidation, decomposition or desulfurization of hydrocarbons and alcohols. Hydrogen derived from electrolysis of water is highly pure, though costly, and hence finds special application as in physic-chemical experiments. Hydrogen for industrial usage such as for starting materials or product refining is in most cases produced by steam reforming or partial oxidation of relatively inexpensive, readily available materials, in which instance steam reforming of light hydrocarbons or alcohols is more often witnessed than partial oxidation of coals or heavy residual oils. Examples of such light hydrocarbons and alcohols include methane, ethane, propane and butane either singly or in combination, and gases containing these hydrocarbons, light naphtha, heavy naphtha and methanol.
Whereas, despite its ease of handling, storage and transport and its low cost, kerosene has not thus far found much use as a source for hydrogen. The main obstacle to this is that it has been economically infeasible to remove sulfur contents from kerosene to a level of concentration (not exceeding 0.2 ppm) tolerable to reforming catalysts which are highly sensitive to sulfur compounds.
A hydrogenative desulfurization process is known for removing sulfur compounds from petroleum oils in the presence of a hydrogen-containing gas by the use of a catalyst such as a cobalt-molybdenum, nickel-molybdenum and nickel-tungsten at elevated temperature and pressure conditions. With this process to reduce sulfur contents to less than 0.2 ppm, it would require pressures above 100 kg/cm.sup.2.G and a liquid per hour space velocity (LHSV) of below 0.1 h.sup.-1 over extended length of time.
It has also been proposed to adsorb sulfur compounds onto metal oxides such as zinc oxide, copper oxide, manganese oxide and iron oxide, but such adsorption method has been experimentally proven hardly possible to maintain a sulfur level below 0.2 ppm.
Reforming processes are employed for removing sulfur contents from a naphtha fraction by adsorption with use of Ni-containing sorbent, but such processes have not thus far been applied to kerosene. The present inventors disclosed a similar adsorption method in Japanese Patent Application No. 61-175322, which method was later found not quite satisfactory because considerable quantities of Ni-containing sorbent are required to achieve the 0.2 ppm level over prolonged length of time.